Extrusion machine



F.- T. GRIFFITHS EXTRUSION MACHI NE Jan. 16,1945.

7 Sheets-Sheet 1 Filed June 30, 1943 r. w w

I G T.

Inventor Hi8 A ltorneyS Jan; 1945- F. T. GRIFFITHS 9 r v EXTRUSIONMACHINE Filed June 30, 1943 7 Sheets-Sheet 2 Frann Z GriffiT/z:

Inventor H is Attorneys Jan. 16,1945;

' F. T. GRIFFITHS 2,367,394

EXTRUSION MACHINE Fi led June so, 1943 '7 Sheets-Sheet 3 FrancisZGriffifhs l I Inventor 8 Attorney;

1945- F. T. GRIFFITHS 2,367,394

' EXTRUSION MACHINE Filed June so, 1943 7 sheets-sheet 4 Inventor B MMLMH is Attorneys Jan. 16, 1945- F. 'r. GRIFFITHS Exmws'lon- MACHINE 7Sheets-Sheet 5 Filed June. 30 1943 E Wwt a,

H 8 Attorney Jan. 16, 1945. GRIFFlTHs 7 2,367,394

EX'I'RUSION MACHINE Filed June 30, 1943 '7 Sheets-Sheet 6 Francis 7.CriF-fif/M Inventor Hi5 Attorneys Jan. 16, 1945.

F. 1'.' GRIFFITHS EXTRUSION MACHINE Filed Jime so, 1943 7 Sheets-Sheet'r Wm No GMT/i772;

Inventor Hi8 A ttofney;

Patented Jan. 16, 1945 EXTRUSION MAC Francis 'lladman Grifliths,Gravesend, Kent, England, assignor to W. T.

Henleys Telegraph Works Company Limited, Dorking, Surrey, England, aBritish company Application June 30, 1943, Serial No. 492.8 50,

in Great Britain July 31, 1942 (Chm-12) 11 Claims.

tending projections and/orrecesses, that relative rotary movement of thetwo members causes material fed into one end of the annular spacebetween them to be fed forward. Continuous relative rotary movement ofthe two concentric members, combined with continuous feeding of thematerial to the impelling device, results in the continuous delivery ofthe material in the plastic state to the extrusionchamber and inextrusion of it through the die or between the inner and outer die, asthe case may be, by the pressure exerted on it by the followingmaterial. It is the practice to arrange the die or, where there is aninner die or point, the two dies, co-axlally with the impelling devicewith the object of pelling devices may ensuring a perfectly uniformpressure at the" mouth of the die throughout the circumference thereof.

In machines of thistype at least one of the members constituting theimpelling device must rotate relative to the main supporting structure.Since a considerable pressure (of the order of ten to twelve tons persquare inch where the ma= terial to be extruded is a metal, such aslead) must be produced in the material in-the extrusion chamber in orderto extrude it. it follows that there will be exerted a correspondinglygreat reaction on the member (or members) that carries the screw threadprojections and/or recesses.

which reaction will have a considerab e component in a directionparallel to the axis of the imp'elling device.

of a thrust bearing which generally requires to be of large dimensionsand of special construction. It is an object of the present invention toprovide an improved form of construction of extrusion machine whichavoids the necessity for such thrust bearings but does not entail thesacrifice to any substantial degree of the qualities as regards uniformextrusion pressure possessed by the existing type of machine in whichthe extrusion orifice is co-axial with the impelling device.

When this member is a rotary member, the thrust must be taken up bymeans In the improved form of construction, the material to be extrudedis delivered to the extrusion chamber by a number of screw threadimpelling devices. These are arranged in pairs, the two de-.

vices of each pair being disposed in axial alignment with each other andwith their delivery ends together. The rotating parts of the two devicesare integral with one another or coupled together at the delivery ends,whereby the thrust on the rotating part of one impelling device of apair opposes thethrust on the corresponding part of the other device ofthe pair, so that, under normal working conditions, the resultant thrustis negligible, and the two or more pairs of devices are distributedround the axis of the extrusion chamber, whereby the material is fedinto the chamber from a number of points distributed around the wall ofthe chamber, so that a substantially uniform feed of material can beobtained throughout the circumference of the extrusion orifice.

The pairs of impelling devices may be distributed around the extrusionchamber axis with their respective axes parallel thereto. Alternatively,the respective axes of the several imbe disposed transversely of theextrusion chamber axis, preferably at right angles thereto. Where themachine has only two pairs of impelling devices, the axes of the twopairs may lie parallel to one another in a plane at right angles to theaxis of the extrusion chamber. Where three pairs of impelling devicesare used, their axes may lie at an angle of to one another and in threeseparate planes at right angles to the axis of the chamber. Where fourpairs are present two pairs may have their axes parallel to each othertwo may have their axes parallel to one another in another plane, forinstance, a plane parallel to the first plane; the axes of the first twopairs for instance, lying at an angle, for instance an angle oi 45", tothose of the other two pairs. In cases where it is necessary to locatethe pairs of extrusion devices in diflerent planes the deliverycharacteristics of the several pairs may b moditied to compensate forthe varying distance from the extrusion orifice.

In. the case of a machine having two pairs of impelling devices disposedon diametrically opposite sides ofthe extrusion chamber with their axesparallel with one another and at right angles to 'that of the extrusionchamber, it is sometimes preferable for the impelling devices andextrusion chamber to be housed in, 'or in part formed by, a machine bodyor casing built up of a pair of end 56 blocks, a pair of cylinders anda' central 'block.

in one plane and the other ures 1 and 2,

Such cylinders each house, or preferably form, the outer parts of one ofthe two pairs of impelling devices, and their ends form spigot andsocket joints with the end blocks in which feed ports are provided whichregister with feed openings in the spigot ends of the cylinders Thecentral block fits between the central parts of the two cylinders andforms or houses the extrusion chamber which is fed from the deliveryends of the impelling devices by ports in its walls which register withdelivery openings in the walls of the cylinders. The assembly ismaintained by tie bolts which draw the two end blocks together.

We also prefer, in some cases, to employ a removable extrusion chamberwhich is externally of cylindrical or substantially cylindrical form,for instance, tapered, and is'arranged to slide axially into a positionin a correspondingly shaped recess o-r'bore in the central part of themachine housing, in which openings in the circumferential wall of thechamber register with ports in the machine housing leading from thedelivery ends of the four or more impelling devices. This removable-extrusion chamber comprises a pair of sleeves which telescope onewithin the other to a limited extent and of which one supports a matrixholder (or a number of such holders) and the other of which has atransverse wall carrying a point holder (or a number oi. such holders)for supporting an inner die or point which may or may not be of tubularform. Preferably, the two sleeves are held together and the completeextrusion chamber secured in place in the recess or bore in the machinecasing by the same clamping means. The chamber may incorporate, betweenthe openings in the circumferent al wall thereof and the matrix, ascreen the bearing 9 formed by the end of the other comprising a supportgrid carrying a layer of wire gauze or other suitable screeningmaterial. This grid is clamped between a'projecting surface on the outersleeve and the inner end of the inner sleeve when the. two parts arelocked in position in a recess'in the machine housing. This grid mayserve as an additional support for the point holder or as the mainsupport.

The invention, which is applicable not only to metal extrusion machinesbut also to machines trusion machine comprising two parallel pairs ofimpelling jdevices, disposed on diametrically opposite sides'of anextrusion chamber and at right angles to the axis thereof. the sectionbeing taken in a plane containing the axes of the said impellingdevices,

- Figure 218 a section. taken on the line II- -II of Fi ure 1 of themachine shown therein,

Figure 3 is a sectional elevation of a second form of construction oflead extrusion machine.

7 Figure 4 is to the left of the centre line a rear elevation andtotheright of the line a front. elevation of a plastics extrusionmachine comprising two pairs or impelling devices arranged gain the leadextrusion machine-shown in Fig- Figu're 51s a sectional-elevation of themachine shown in Figure. 4,

Fi ur 6 is a section taken'on the unevr-vr of Figure .5,

Figure 7 is a section, on an'enlarged scale, taken onthe line VII-VII ofFigure 5, and

Figure 8 is a fragmental section, on a still larger scale, on the lineVIII-VIII of figure 5 showing the machine fitted with a multiple dieextrusion chamber in place of the single die chamber shown in Figures 4,5 and 7.

The machine shown, somewhat diagrammatically, in Figures 1 and 2 of thedrawings is intended for the'production of tubing of lead or lead alloyor for the sheathing of electric cable with such metal. It comprises amachine casing l in the form of a pair of barrels integral with acentral part having an aperture which extends from the front to the rearface thereof and at right angles to the two barrels. The central part ofthis aperture is of increased diameter to form an extrusion chamber 2.An outer extrusion die or matrix 3 is fitted in one of the portionsadjacent the enlarged portion 2 of the aperture and is held in .place bya tubular nut 4 screwing into the wall of the aperture. The other orrear end of the aperture receives a tubular nut 5 constituting a holderfor an inner die or pointfl which passes centrally through the extrusionchamber 2. The barrels 1 are parallel to one another symmetrical about avertical plane containing the axis of the extrusion chamber, and arelocated oneabove and one below the central aperture and directly aboveand below the extrusion chamber 2, but they may, alternatively, lie tothe rear of that chamber. Each barrel 1 is counterbored at each end toreceive a bush 8, the outer end of which forms a bearing 9. Each hushedbarrel houses-a shaft in extending from the bearing 9 formed by one bushto and beyond .bush. The overhanging end of each shaft l0 carries a gearwheel H by which a drive may be imparted to it. Additional hearings tosupport this end of each shaft may be provided. Portions of each shaftthat lie one on each side of a central portion of the barrel I areprovided with a screw thread II, the thread on one portion being ofopposite hand to that on the other portion. -T'hese threads, which maybe single-start or multi-start threads, (the former being shown)co-operate with the adjacent surfaces of the tubular barrel linings 8 toform-screwthread impelling devices. The threads are-preferably of thebuttress form shown in Figure 1 and lie at an angle of about 85 to theaxis of the shaft, and the surfaces co-operating with them haveprojections or recesses, for instance, a screw thread l3 of oppositehand'to that on the adjacent part of the shaft, or are rifled or groovedlongitudinally. Alternatively, the barrel linings 8 may be screwthreaded and the co-operating surface of the shaft be splined.

At the outer end of each bush 8 an annular feed chamber I4 is formed byincreasing the clearance between the shaft in and the bush, andprovision is made for feeding the chamberwith molten metal. The feedchamber I4 is heated by means of electric'heaters in the wall of thebarrel,

located as shown diagrammatically at ii, to maintain the metal in thechamber in the mblten condition. In the central region of each impellingdevice circumferential channels i8 are provided in and around the wall,of thebarrel through whicha cooling medium, for instance.

air, steam or water, may be jcirculated'to cool machine, it is not soconvenient.

. 2,867,894 end of the device. Between the-feed chamber ing and theadjacent end of each internally screw threaded bush,'the wall of thebarrel is smooth and the clearance between it and the screw threadedshaft forms an annular,delivery chamber I9. Each of these four annulardelivery chambers I9 is placed in communication with the extrusionchamber 2 by a separate port 20, the ports from the four chambersentering the IB of each shaft separating details from the lead extrusionmachine described above with reference to incorporates certain novelfeatures of construction' which are not present in the lead machineshown in Figures 1 and 2 but may, nevertheless, in some cases, beincorporated in such a machine.

- Referring now more particularly to Figures 4, 5

and 6, it will be seen that the casing'is built up of a pair of endblocks 3!, a pair of cylinders 32 and a central block 33. The ends ofthe cylinders enter recesses 34 in the end blocks and are held thereinby four tie bolts 35 which draw the two end blocks together. The centralblock common extrusion chamber at points more or less uniformlydistributed around the circumferential wall thereof. -At each end of thecentral bearing surface on each shaft it is preferred to provide ascrew'thread gland 2| for building up a counterpressure; in any metalentering the bearing, which will prevent transfer of plastic metalacross the bearing. Alternatively, this central hearing may be omittedand the shaft be locally reduced in diameter to provide one deliverychamber for each pair of axially aligned impelling devices which can beplaced in communication with the transversely extending extrusionchamber by a single port. With such an arrangement; plastic metal wouldbe fed into the extrusion chamber at diametrically opposite sidesthereof.

. It will generally be necessaryv to apply heat in the region of thedelivery ends of the impelling 83 is of general rectangular form and islocated between parallel surfaces 36 on the central portion of thecylinders 32. These surfaces are flat except for recesses 31 in whichenter correspondingly shaped projections 38 in the co-operating surfacesof the block and serve Positively to restrain the central bloc]; frommoving relatively to the cylinders. Alternatively, of course, theprojections may be on the cylinders and the recesses in the wall of theblock. In addition, the

. central block 3| may be held between the two devices and that of theextrusion chamber. This may be effected'very conveniently by insertingtubular electric heaters 22 in the necessarily massive walls of thebarrels I and those of the extrusion chamber 2. I

The lead extrusion machine shown diagrammatically in Figure 3 of thedrawings resembles that described with reference to and shown in Figures1 and ,2, save as regards the disposition of the extrusion chamber.Consequently, the same reference numerals have been used to in-. dicatecorre ponding parts in the two machines; In the machine shown in Figure3, the axes of the two pairs of impelling devices are parallel with, andlie one on each side of, that of the extrusion chamber. The machine bodyin this case, however, is in the form of a triple barrelled block. Asregards the elimination of heavy thrust bearings and symmetry of feedinto the extrusion chamber, the machine is the equivalent of that shownin Figures 1 and 2, but, as regards control of the temperature of thevarious parts of the The machine shown in Figures 4 to '7 of thedrawings is of the same general form as that shown in Figures 1 and 2,that is to say, it has two pairs of screw thread impelling devices, eachof atype in which the inner of the two longitudinally extendingconcentric members is rotatably driven, the two devices of each pairbeing in axial alignment and having their respec tive rotating partsintegral with one another atthe delivery ends, the two pairs'beingdisposed on diametrically opposite sides of the extrusion chamber withtheir axes parallel with one another and at right angles to that of theextrusion chamber. However, it has been developed for the extrusion ofsyntheticplastics such as, for instance, polyvinyl chloridecompositions, and differs in cylinders by transverse tie bolts extendingfrom cylinder to cylinder. These may or may not pass through the centreblock. Alternatively, the flat surfaces 36 on the cylinder may beslightly inclined to one another and the central blockbe given in acorrespondingly slight tapered form so that it may be wedged in positionto ensure a tight joint between the co-operating surfaces. Theseprecautions to. obtain a tight joint between the co-operating surfacesof the block and cylinders are not necessary where the machine is to beused on rubber or plastics but may be advisable in the case of leadmachines in whichthe extrusion pressures required are very much higher.

The cylinders 32 of of the barrels I and their linings 8 of the leadmachine described above and form the outer concentric members of theimpelling devices. -Where the material to be extruded is rubberor asynthetic plastic, the bore of the cylinders may be smooth as shown andof the same diameter throughout the length thereof, but naturally, ifthis built up machine casing construction is adopted for a leadextrusion machine, the bore will have, except possibly at its centre, abroken surface of a kind described above with reference to Figures 1 to3 of the drawings. The inner concentric member of each pair of axiallyaligned impelling devices is, as in the case of the lead machinepreviously described, constituted by a shaft, 40, of which the portionslying within the cylinder and to each side of a central portion 4|serving as a central bearing carry each a screw thread 42, the thread onone portion being of opposite hand to that on the other. As

the machine shown in Figures 4 to 7' is for plastics, the angle of thethread is advantageously about 75 to Each end of each shaft 4il'projectsthrough a bushed opening 43 in the bottom wall of the recess 34receiving, the spigot end of its cylinder 32 and is rotatably supportedby a ball bearing 44 housed in a bracket 45 extending from the end block3!. This is preferable to housing thebearing in the block itself as itreduces the flow of heat to the bearing.

In each end block M are provided a, pair .of feed ports 46, one for eachimpelling device, which register with feed openings 41 in the spigotends of the cylinders 32. Delivery openings 48 are provided in the wallsof the cylinders Figures 1 and 2. It also 1 this machine take the place:2 which register with delivery ports 49 a the wall of the central block85 and serveto place the four annular delivery chambers 58 incommunication with a removable extrusion chamber 5| housed in thecentral block. This extrusion chamber, as will be seen most clearly fromFigure 7 of the drawings, is built up of a pair of sleeves 52, 53 whichtelescope one within the other to a limited extent. The sleeves are ofcir cular cross-section and the outer, 52, is a push-in fit in acylindrical bore 54 of corresponding crosssectional shape which extendsthrough the central block 33 in a direction at right angles to the axesof the cylinders 32 and their impeller shafts 40. At one end the outersleeve 52 has an outwardly turned flange 55 which bears against thefront face'55 of the block 33. At its other end it has an inwardlyextending flange which is integral with a tubular part 51, concentricwith,

but of considerably smaller diameter than, the sleeve, and extendingaxially towards the flanged end to form a support for an inner die orpoint 58 which is a sliding fit in the end of the holder 51. At its endcarrying the flange 55 the outer sleeve is counter-bored to a largerdiameter and to a depth extending just to the rear of the front end ofthe point holder 51 to provide an annular seating 59. The inner sleeve53 is a sliding fit in the counter-bored part of the outer sleeve 52,projects outwards beyond the flanged end of the outer sleeveand alsocarries an external flange 50 which overlies the flange 55. The wallthickness of the sleeve 53 first increases rapidly as the outer end ofthe sleeve is approached, to provide a conical surface 5|, and thengradually diminishes to provide a conversely tapering surface 52 whichforms a seating for an outer die or matrix 53 which is held in place byan annular cap 54 screwed on the ring shaped projection 55 formed bycutting an annular groove in the front end face of the sleeve. The innerend face of this matrix forms a continuation of the conical surface 5|of the inner sleeve. Four openings 55 are provided in the wall of theouter sleeve.

These are located between the inwardly extend- I engaging the front face55 thereof. Between the inner end of the inner sleeve and the annularseating 59 i the outer sleeve is located a screen consisting of .aforaminous disc 51 with an external diameter equal to that of the innersleeve, and of a gauze disc 58 of slightly less diameter housed in arecess in the disc. Both disc and gauze have central apertures in whichthe front end of the point holder, which in this region is cylindrical,is a sliding fit. The inner sleeve 53 is pressed inwardly to clamp thescreen between it and the seating 59 and to hold the outer sleeve 52 intheblock, by means of a number of hand clamps 59 mounted on studsprojecting from bosses on the front face 55 of the block, one

1 in each corner thereof. These have cam faced jaws which normallyengage the front face of the flange 50 on the inner sleeve, but canreadily be swung clear to permit removal of the inner sleeve and thescreen, or, if required, of the entire extruslon chamber. To provide forlongitudinal adjustment of the point 58 it is screw threaded internallyand receives a tube which extends rearwardly beyond the rear end wall ofthe outer sleeve 52 and is restrained from moving axially .of the pointholder by means of its collar 1i and the retaining ring 12. By rotatingthe sleeve and preventing the point from rotating relative to its holderby means of a feather key or the like, the latter may be movedlongitudinally whilst the machine is working, thereby permitting thewall thickness of the extruded product to be corrected without delay. V

In a modified form of construction of removable extrusion chamber, thematrix holder is adjustably positioned in one end of the outer sleeveand the point holder is integral with the inner sleeve. In this form theoverlapping parts of the sleeves lie on the opposite side of the screento the matrix -holder and, consequently, the apertures which registerwith the delivery ports in the wall of the block housing the sleeves arein this double walled portion of the extrusion chamber. Also theexternal flanges on the outer and inner sleeves lie at the rear, so thatthe chamber is inserted from the opposite direction to that in which thechamber shown in Figure 7 is inserted.

The provision of a central bearing M for the two impeller shafts 40which separates the neighbouring delivery chambers 5!] permits of theproduction of a partiscoloured rubber or plastic product by chargingeach impelling device with stock of an appropriate colour. To this endthe annular extrusion chamber may be divided into four compartments byradially extending partition walls which maintain the stock delivered byeach port 49 separate from that delivered by the others. Thesepartitions may be permanent or removable. Partitions of the latter formare shown in the upper half of Figure '7, but are omitted from the lowerhalf for the sake of clearness. They comprise a pair of flat plates. Oneplate, 13, of each pair is located to the rear of the screen and midwaybetween two neighbouring ports by engaging in grooves in the wall of theouter sleeve 52 and in the surface of the point holder 51. The otherplate, 14, is located between the screen and the matrix and is locatedin alignment with the plate 13 by engaging in grooves in the conicalsurface of the inner sleeve'53 and in the surfaces of the point 58 andpoint holder 51, thus also serving to restrain the point from rotatingrelative to its holder. The plastic material delivered to the extrusionchamber thus progresses therethrough in four separate streams of arcuatesection separated only by the thickness of the partition walls (whichcan be small, since there is no appreciable pressure difference acrossthem) until just before they reach the extrusion orifice, between whichpoint and the oriflce they unite without appreciable interpenetration.

The single oriflce extrusion chamber shown in Figures 4, 5 and '1 of thedrawings may be modifled, as shown in Fig. 8, to provide for two or moreextrusion orifices. The form of the inner telescoping sleeve is similarto that shown in Figure '1 save that it is fitted with a removable frontwall which provides for the mounting of a pair of dies 53. The method ofmounting them, however, is precisely the same. The internal form of theouter sleeve 52 is rather difierent in that massive point holders whichextend from the rear end wall are dispensed with and the foraminous disc51 is provided with a pairof tubular projections 15 which serve the samepurpose. This has the advantage of reducing to a minimum the obstructionpresented to the stock as it issues from the openings 55 in thecircumferential wall of the chamber. To ensure correct alignment ofpoint and die, a projection is provided on the end of which engages in arecess in the and a key 18 on the flange 55 of the outer sleeve toengage in a slot in the flange 60 of the inner sleeve. Naturally, theinterior of this modified form of removable extrusion chamber may befurnished with removable division plates to confine the stock from eachimpelling device to a particular extrusion orifice or, where more thantwo sets of dies are present, to a particular orifice or group oforifices. One pair of such plates is shown at 16 and II in Figure '8. Itwill beappreciated that the provision, of more than one die will entailsome sacrifice as regards uniformity of extrusion pressure, particularlywhen division plates are present.

Withdrawal of the removable extrusion chamthe inner sleeve rim of thegrid 67 tion of the need for heavy her is facilitated by an extractorcomprising a four legged table 80 with a screw threaded aperture inwhich works a screw threaded rod 8| carrying a rotatable cup 82 of whichthe rim is rear face of the outer sleeve 'chamber- The feet 83 of theadapted to fit the 52 of the extrusion extractor seat on sleeves 84on'the tie bolts 35 and are held there by a handle 85 secured to thebush and having areduced portion 86 which enters a circumferentiallyextending slot 81 in the foot, as is most clearly shown in Figure 8. Byscrewing down the rod by rotating the hand wheel 88, the inner and outersleeves are pushed out of the bore in the central block and the fourstreams of plastic material in the delivery ports 49 and 66 are shearedthrough.

For the satisfactory extrusion of a plastic such as a polyvinyl chloridecomposition, it is generally necessary to apply heat to the delivery endof the impelling device and in the region of the extrusion chamber. Inthe machine shown in Figures anced pairs of impelling devices,.possesses a number of advantages in addition to the elminathrustbearings without sacrifice of uniform extrusion pressure. The rotatingmember of each impelling device can,

if required; be supported at its delivery end with-- out introducing -abearing of which the ends are subject to large pressure difierences.This is particularly important in the case of lead extrusion machineswhere the pressure at the delivery end is 10 to 12 tons per square inch.In the case of a lead extrusion machine, the improved form ofconstruction eliminates trouble arising from oil lubrication of movingparts subject to high temperature, for, as all gearing is extraneous tothe machine, the only moving parts subject to high temperature are thethree bearings for each rotating member, and each of these iseffectively lead lubricated. The inner part of each impellingdevice canbe cooled internally; if necessary, as no provision has to be made forthe passage through it of a cable or other core to which a covering ofthe extruded material is 4 to 8 of the drawings, the parts ofeach'cylinder between the end blocks 3| and the central block 33 areexternally of-octagonal cross-section to provide flat surfaces 90 onwhich electric resist- I anoe heating elements 9| are clamped, andtubular electric heaters 92 are inserted in the wall of the centralblock in which'the removable extrusion chamber is housed. Naturallythese heated parts of the machine casing are encased in heat insulatingmaterial. to reduce loss by radi ation. Provision is made to measure theternperature of the stock at the feed ports 46 by thermostats 94 and atthe extrusion chamber by a thermostat 95. For the extrusion of naturalrubber mixes by a machine ofv the form shown in Figures 4 to 8, theheating arrangements there shown would be replaced by suitable coolingarrangements, for instance, a water jacket or channels for thecirculation of a cooling liquid, generally water.

It will be noticedthat, at one end, each shaft 40 is supported in thebearing 4| through an intermediary consisting of the socketed end of adriving shaft 96. This shaft 96 is supported at its other end by asecond bearing 81 mounted on a pedestal 98 and carries a driving wheel99 on its overhanging end. The end of the shaft 40 fits into the socketof the shaft 96 with a morse taper fit and is held in driving engagementby means of the screwed bolt I00 whichalso provides a means ofdisengaging the two shafts. When disengaged, the impeller shaft 40 maybe withdrawn from the opposite end of the machine casing without havingto dismantle the gear drive thereto. s

From the preceding description, it will be appreciated that the improvedconstruction of extrusion machine, comprising two or more balto beapplied. Where an inner die or point is used, this can be mounted morerigidly as its support is isolated from all moving parts and is notrequired to be lengthened for the purpose of providing an impellingsurface, or a surface cooperating with an impelling surface, as in manyexisting types of machines, The use of a short support for the pointpermitsof bridge pieces extending from the support to the wall of theextrusion chamber to be dispensed with and has the additional advantagethat the length of cable in the machine at any time is a minimum. Thislatter is of importance in the lead sheathing of impregnated paperinsulated cables, for there is then no danger of the cable being damagedby over heating. In the usual forms of construction of extrusion machinefor the production of lead tube or cable sheathing, Provision has to bemade for adjustment of the outer die or matrix with respect to the innerdie in order to secure control of the wall thickness of the product.With the improved machine constructed in accordance with the presentinvention, the wall thickness may be controlled by adjusting the flow oflead from the several impelling devices into the extruson chamber,-rendering unnecessary the provision of die adjusting means.

What I claim as my invention is:

1. A,machine-for the extrusion of material in a highly viscous orplastic state, comprising to feed in material through a number ofopenings distributed around the wall thereof.

2. A machine for the extrusion of material in a highly viscous orplastic state, comprising an extrusion chamber with an extrusion oxificeand two pairs of screw thread impelling devices for delivering materialto the chamber, each device comprising two longitudinally extending andrelatively rotatable concentric parts, the two dev'ces of each pairbeing in axial alignment with their delivery ends together and havingtheir respective rotating parts united at their deliiery ends, and thetwo .pairs of devices being disposed on opposite sides of the extrusioncham-, her with their axes parallel to one another and at right anglesto that of the extrusion chamber,

relatively rotatable concentric parts, the two devices of each pairbeing in axial alignment with their delivery ends together and havingtheir respective rotating parts united atthe delivery ends, and the twopairs of devices being disposed on opposite sides of the extrusionchamber with their axes parallel with that of the extrusion chamber,whereby to feed in material-through a number of openings distributedaround the wall thereof.

4; A machine for the extrusion of material in a highly viscous orplastic state, comprising a pair of end blocks, a pair of cylindersdisposed in spaced parallel relationship and extending between said endblocks and making spigot joints therewith, a central block fittingbetween the central parts of said cylinders and making joint therewith,an extrusion chamber in said central block having an extrusion orificein an end wall thereof, a pair of axially aligned screw thread impellingdevices in each of said cylinders, the feed ends of said devices beingat the ends of said cylinders and the delivery ends at the middlethereof, the end blocks having feed openings which register with lateralfeed openings in the spigot ends of said cylinders, and the centralblock having ports which register with delivery openings in the walls ofsaid cylinders and place said extrusion chamber in commumcation withthedelivery ends of said impelling devices.

r 5. A machine for the extrusion of material in a highly viscous orplastic state comprising an extrusion chamber with an extrusion orifice,at least two pairs of screw thread impelling devices distributed roundthe said chamber, each device having its own separate delivery chamberand comprising two longitudinally extending and relatively rotatableconcentric parts, the

wall of the surrounding barrel, located one of each side of the centralbearing, a separate por between each delivery chamber andthe saidextrusion chamber, the said ports from the deliver: chambers enteringthe extrusion chamber a1 points distributed around the circumferentialwall thereof, and means for driving each of sale impeller shafts 'inrotation within its barrel ir. a direction to impel plastic material inthe barrel into each delivery chamber and thence through said ports intothe said extrusion chamber.

7; An extrusion machine comprising a machine body including a centralportion and a pair of barrels disposed symmetrically on opposite sidestwo devices of each pair being in axial alignment with their deliveryends together and having their respective rotating parts "united attheir delivery ends, and a separate port from each delivery chamber tothe extrusion chamber, the ports from all the delivery chambers enteringthe common extrusion chamber at points distributed round thecircumferential wall thereof.

6. An extrusion machine comprising a machine body including a centralportion and a pair of barrels disposed symmetrically on opposite sidesof said central portion with their axes parallel to one another, anextrusion chamber in said central portion, a pair of impeller shafts,one in of said central portion with their axes parallel to one another,an extrusion chamber in said central portion, a pair of impeller shafts,one in each barrel, a pair of screw threads on each of said shafts, thescrew threads of each pair being of opposite hands and disposed one oneach side of a central portion of the surrounding barrel, which portionforms a central bearing for the shaft therein, surfaces on the internalwall of each barrel which co-operate with the screw threads on the shafttherein to form a pair of screw thread impelling devices, annulardelivery chambers between each of said shafts and the wall of thesurrounding barrel, located one on each side of the central bearing, aplurality of separate ports, one between each delivery chamber and thesaid extrusion chamber, the said ports enter ing the said extrusionchamber at points distributed around the circumferential wall thereof,means for driving each of said impeller shafts in a direction to impelplastic material in the barrels into the delivery chambers and thencethrough said ports into said extrusion chamber, and at each end of thecentrallysupported portion of each impeller shaft a screw thread ofopposite hand to thatof the adjacent impelling thread on that shaft andof relatively short pitch, for building up a counterpressure in materialentering the bearing from the delivery chamber adjacent to it.

8. In an extrusion machine comprisin a machine body housing a number ofpairs of screw I thread devices for impelling material in a highly eachbarrel, a pair of screw threads on each of said shafts, the screwthreads of each pair being of opposite hands and disposed one on eachside "of a central. portion of the surrounding barrel,

- which portion forms a central-bearing for the shaft therein, surfaceson the internal wall of each'barrel which co-operate. with the screwthreads on the shaft therein to form a pair of screw thread impellingdevices, annular delivery chambers between each of said shafts and theviscous or plastic state, each device comprising two longitudinallyextending and relatively rotatable concentric parts and the two devicesof each pair being in axial alignment with their delivery ends togetherand having their respective rotating parts integral with one another orcoupled together at the delivery ends, an extru sion chamber comprisinga pair of sleeves which telescope one within the other to a limitedextent, an end wall on one of said sleeves for supporting a matrix, anend wall on the other of said sleeves supporting a holder for an innerdie, the outer of said sleeves being of substantially cylindrical formand a sliding fit in a correspondingly shaped hole in a central part ofsaid machine body and the circumferential wall of said chamber having aplurality of openings which register with ports in the machine bodyleading from the delivery ends of the said screw thread impellingdevices.-

tatable concentric parts. and the two devices of each pair being inaxial alignment with their delivery ends together .and having theirrespective rotating parts united at the .delivery ends thereof, anextrusion chamber having openings in its circumferential wall, removablypositioned in the central part of said machine body with said openingsregistering with ports in the machine body leading from the deliveryends of the said screw thread impelling devices, said chamber comprisinga pair of sleeves which telescope one within the other to a limitedextent, one of said sleeves having an end wall for supporting a matrixand the other of said sleeves having an viscous or plastic state, eachdevice comprising two longitudinally extending and relativelyrocircumferential extrusion chamber into at least two segmental parts,said dividing means comprising a corresponding number of partition wallswhich are preferably removable and which each extend between the innerdie and its holder and the wall or the chamber, the said being solocated with respect to partition walls the circumferential wall of thethe opfinings in chamber that each delivery port feeds only onesegmental part of the partitioned chamber.

11. in an extrusion machine comprising a machine body housing a numberor pairs oi screw thread devices i'or impelling material in a highlyviscous or plastic state, each device comprising two longitudinallyextending and relatively rotatable concentric parts and the two devicesof each pair being in axial alignment with their delivery ends togetherand having their respective rotating parts unitedat the delivery endstatable concentric parts and the two devices of each pair being in axialalignment with their delivery ends together and having their respectiverotating parts united at the delivery ends thereof, an extrusion chamberhaving openings in its circumferential wall, removably positioned in thecentral part of said machine'body with said openings registering withports in the machine body leading trom the delivery ends of the saidscrew thread impelling devices, said chamber comprising a pair ofsleeves which telescope one within the other to a limited extent, one orsaid sleeves having an end wall supporting a matrix and the other an endwall supporting a holder thereof, an extrusion chamber having openingsin its'circumferential wall, removably positioned in the central part ofsaid machine body with said openings registering with ports in themachine body leading from the delivery ends or the said screw threadimpelling devices, said chamber comprising a pairoi sleeves whichtelescope one within the other to a limited extent, one of said sleeveshaving an end wall supporting two mat- ,rices and the other an end wallsupporting a pair 0! holders for inner dies eo-operating with thematrices, and means comprising a partition wall,

which is preferably removable and which passes across the chamberbetween the two holders, for dividing the chamber into two parts eachhaving for an inner die, and means for dividing said the same number orthe registering openings as the other.

FRANCIS TADMAN GRIFFITHS.

- I Disclaimer 7 ,394.Franaz's Tadman Grifliths, Gravesend, Kent,England. Ex'rRUsmN MACHINE. Patent dated Jan. 16, 1945. Disclaimer filedDec. 12, 1949, I by the assignee, W. T.- Henleys Telegraph Works CompanyLimited.

Hereb enters this disclaimer to claims 1 and 2 of said patent. cialGazette January 3, 1950.]

